This invention relates in general to vehicle seats, and in particular to vehicle seats having adjustable lumbar systems. Vehicle seats typically include a seat back and a seat cushion or bottom. The seat back is often pivotally mounted to the seat bottom via a recliner mechanism for adjusting the seat back to a desired inclined angle relative to the seat bottom. Known recliner mechanisms are either manually operated or may include a motor drive unit for electric operation. The seat bottom may also be configured to move the seat in fore and aft directions as well as in a generally vertical direction. Other comfort features include a lumbar mechanism mounted in the seat back. The lumbar mechanism is operated by the seat occupant to adjust the shape and contour of a portion of the seat back to provide a desired support level and comfort position for the seat occupant. Generally, the lumbar mechanisms are provided for altering the contour of a central region of the seat back. The lumbar mechanisms are generally mounted underneath the outer trim cover and foam pads of the seat back. Some lumbar mechanisms provide a fore and aft adjustment, as well as vertical adjustment of the lumbar mechanism.
Known lumbar mechanisms include mechanical systems and inflatable systems. An example of a mechanical system uses deflectable or bowed members generally having a curved shape. To adjust the fore and aft position, the members can be moved outwardly or inwardly relative to the central region of the seat back. Such a lumbar mechanism is disclosed in U.S. Patent Application Publication No. 2007/0132296. Additionally, the bowed members may be moved in a generally vertical direction along the height of the seat back. Inflatable systems can be pneumatic or hydraulic and use one or more inflatable bladders mounted underneath the trim cover and the foam pads of the seat back to function as an adjustable lumbar mechanism. Such a system is disclosed in U.S. Pat. No. 5,562,234. To alter the contour of the seat back, one or more of the bladders are selectably expanded or contracted to provide the desired contoured shape of the seat back.
It is also known to provide either mechanical or inflatable lumbar systems with memory systems for storing and retrieving desired lumbar positions. The seat occupant moves the lumbar mechanism to a desired position and operates a control device for storing information regarding the current position of the components of the lumbar mechanism. The control device is a microprocessor which stores and retrieves this positional information. If the lumbar mechanism has been moved from this preferred stored position, the seat occupant need only to operate the controller to select the stored memory position and the controller will automatically operate the lumbar mechanism until the respective components are back at that desired stored position. For example, in the mechanical lumbar systems, the control device stores information regarding the position of the bowed lumbar member relative to fixed structures within the seat back. For inflatable systems, a pressure sensor is often used to store the desired pressure within each of the bladders. The controller can than operate various valves and pumps or fluid devices to set the internal pressure of the bladders at the selected pressure. Although these memory systems are helpful, they do not account for temperature or wear variations over time of the outer trim cover and the foam of the seat back.